Global Navigation Satellite Systems (GNSS) include the Global Positioning System (GPS), the Globalnaya Navigatsionnaya Sputnikovaya Sistema (GLONASS) system, the proposed Galileo system, and the proposed Beidou system. Receivers from multiple manufacturers are now commercially available which can receive and process signals from satellites of multiple GNSS, such as GPS and GLONASS. Users are particularly interested in being able to mix and match reference and rover receiver hardware from different manufacturers. In many cases, a customer may not own the reference station being used to generate correction data, and may not know which receiver type is generating the available correction data. Receiver hardware of different types, e.g., from different manufacturers, may not be compatible.
Several authors have investigated the problems faced when performing GLONASS carrier phase ambiguity resolution, such as: Habrich, H., Beutler, G., Gurtner, W. & Rothacher, M. (1999) Double difference ambiguity resolution for GLONASS/GPS carrier phase. 12th Int. Tech. Meeting of the Satellite Division of the U.S. Inst. of Navigation GPS ION'99, Nashville, Tenn., 14-17 September, pp. 1609-1618; Han, S., Dai, L., & Rizos, C., (1999) A New Data Processing Strategy for Combined GPS/GLONASS Carrier Phase-Based Positioning, 12th Int. Tech. Meeting of the Satellite Division of the U.S. Inst. of Navigation GPS ION'99, Nashville, Tenn., 14-17 September, pp. 1619-1627; Wang, J., Rizoz, C., Stewart, M. P., & Leick, A., (2001) GPS and GLONASS Integration: Modelling and Ambiguity Resolution Issues, GPS Solutions, vol. 5. no. 1. Summer, pp. 55-64. These publications do not address the estimation of GLONASS code and/or carrier biases between data collected by receiver hardware of different types.
Improved methods and apparatus for processing GNSS signals are desired, particularly to enable compatibility between receivers of different types.